Structural diversity of dietary fatty esters of chloropropanols and related substances

Effects of deodorization temperature and time on the formation of 3-MCPD, 2-MCPD, and glycidyl esters and physicochemical changes of palm oil

This study verified the formation profile of esters of 3-monochloropropane-1,2-diol (3-MCPDE), 2-monochloropropane-1,2-diol (2-MCPDE), and glycidol (GE), and evaluated the physicochemical changes (free-fatty acid, acylglycerols, and colour) that occurred during the deodorization of palm oil in different conditions of time (30, 60, 90, and 120 min) and temperature (210, 230, 250, and 270 °C). Levels of 3-MCPD and 2-MCPD esters ranged from 1.91 to 2.70 mg/kg and 0.68 to 1.44 mg/kg, respectively, and were formed at the mildest tested condition (210 °C, 30 min). No correlation was observed between these contaminants and physicochemical changes. GE levels varied from 0.12 to 8.51 mg/kg and showed correlation with color and diacylglycerol content. While the temperature had little influence on the formation of esters of 3-MCPD and 2-MCPD, the content of GE considerably raised above 250 °C.

Synthesis of 2-Monochloropanol Fatty Acid Esters and Their Acute Oral Toxicities in Swiss Mice

A novel synthetic route was designed, developed, and utilized to synthesize six high-purity 2-monochloropropanediol fatty acid esters (2-MCPD esters), a group of potential processing-induced food contaminants. A chlorine atom was introduced to C-2 of a diethyl malonate molecule, which was reduced by NaBH₄ and followed by esterification using fatty acids. The reaction products were isolated and purified using silica gel columns to obtain three 2-MCPD monoesters and three diesters at about 50-54% and 56-59% yields, respectively. In addition, 2-MCPD monopalmitate and dipalmitate were examined for their acute oral toxicities in Swiss mice. The LD₅₀ values of 2-MCPD mono- and dipalmitate were greater than 5000 mg/kg body weight (BW), along with detectable nephrotoxicity and testicular toxicity. The results of this study may promote future investigation of MCPD ester toxicology and detection.

Washing bleached palm oil to reduce monochloropropanediols and glycidyl esters

The formation of toxic compounds, potentially carcinogenic, during food processing has been considered an important food safety issue. Among them, particular attention has been given to 3-monochloropropane-1,2-diol esters (3-MCPDE), 2-monochloropropane-1,3-diol esters (2-MCPDE) and glycidyl esters (GE), which can be formed during vegetable oil refining, especially palm oil. These substances may pose a health risk to humans due to their toxicity and carcinogenicity. The aim of this study was to investigate the effect of washing bleached palm oil (BPO) with different solvents, and evaluate the reduction of 3-MCPDE, 2-MCPDE and GE as well as assess the quality parameters of the final product. For this purpose, we used two types of washing with different solvents. A single washing was carried out in one step and a double washing in two steps using a solvent gradient. Single washing had a limited reduction in the levels of 3-MCPDE and 2-MCPDE and resulted in an increased level of GE, whereas double washing slightly reduced 3-MCPDE and 2-MCPDE and resulted in a significant reduction of GE levels. The reduction achieved in this study was up to 17.1% for 3-MCPDE, 56.4% for 2-MCPDE and 76.9% for GE levels. The reduction of 3-MCPDE and 2-MCPDE might be due to the removal of part of the ethanol-soluble chlorinated precursors from the oil which suggests that highly lipophilic forms of these substances are present in BPO. The substantial reduction on GE levels might be associated with the removal of the precursors present in the oil such as diacylglycerols. Thus, the washing treatment could be used as a supplementary strategy to reduce processing contaminants from palm oil, especially GEs.

An investigation of presence of 2- and 3-monochloropropanediol fatty acid esters in Canadian human milk samples

Occurrence of 2- and 3-monochloropropanediol fatty acid esters (MCPDEs) in 199 human milk samples collected from Canadian women was examined in this study. MCPDEs were determined via indirect analytical approach by using acidic hydrolysis/transesterification and derivatization with cyclohexanone using a fluorinated sulfonic acid resin as a catalyst followed by GC-MS analysis. Analyses were done by a stable isotope dilution assay (SIDA) using 3-monochloropropanediol-d₅ dipalmitate and 2-monochloropropanediol-d₅ distearate as internal standards. In all samples 2-MCPD esters were not detected, at LOD = 1 ng/g for 2-MCPD equivalent. 3-MCPD esters were not detected, at LOD = 2 ng/g for 3-MCPD equivalent, in 193 samples. Six samples had the apparent concentration of 3-MCPD equivalent in the range of 2.0-5.1 ng/g, which was likely caused by accidental contamination during processing of samples. For selected samples, these findings were confirmed by direct analysis via LC-MS/MS analysis based on SIDA for 3-MCPD dipalmitate and 2-MCPD distearate. To our best knowledge, this is the first study to analyze human milk samples for 2-MCPD esters.

Time-course and molecular mechanism of hepatotoxicity induced by 1,3-dichloro-2-propanol in rats

This study investigated the time-course of 1,3-dichloro-2-propanol (1,3-DCP)-induced hepatotoxicity and the molecular mechanism of its oxidative stress and apoptotic changes in rats. Thirty-six male rats were randomly assigned to six groups of six rats each and were administered a single oral dose of 1,3-DCP (90 mg/kg) or its vehicle. 1,3-DCP caused acute hepatic damage, as evidenced by marked increases in serum aminotransferase, alkaline phosphatase, and histopathological alterations. These functional and histopathological changes in the liver peaked at 12h after administration and then decreased progressively. Oxidative stress indices were increased significantly at 6h, peaked at 12h, and then decreased progressively. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)- and caspase-3-positive cells increased after 6h, peaked at 12 and 24h, and then decreased. The protein levels of phosphorylated mitogen-activated protein kinases (MAPKs) including p-Erk1/2 and p-JNK showed a similar trend to the numbers of TUNEL- and caspase-3-positive cells. These results indicate that 1,3-DCP increases oxidative stress, nuclear translocation of Nrf2, and expression of Nrf2-targeted genes, followed by increased functional and histopathological alterations in the liver. The increase in hepatocellular apoptosis induced by 1,3-DCP may be related to oxidative stress-mediated MAPK activation.

Determination of 3-monochloropropane-1,2-diol fatty acid esters in Brazilian vegetable oils and fats by an in-house validated method

An in-house validated GC-MS method preceded by acid-catalysed methanolysis was applied to 97 samples of vegetable oils and fats marketed in Brazil. The levels of the compounds ranged from not detected (limit of detection = 0.05 mg kg(-1)) to 5.09 mg kg(-1), and the highest concentrations were observed in samples containing olive pomace oil and in products used for industrial applications, such as palm oil and its fractions (olein and stearin). The content of diesters and monoesters was also investigated by employing solid-phase extraction on silica cartridges, indicating that the majority of the compounds were present as diesters. This study provides the first occurrence data on these contaminants in Brazil and the results are comparable with those reported in other countries.

Isotope labeling studies on the electron impact mass spectral fragmentation patterns of chloropropanol acetates

Chloropropanol (CP) esters are part of an emerging group of process-induced toxicants that are considered as potential health hazards particularly in palm oil. Mass spectrometry-based methodologies for identification of CP esters in food are critical in overcoming the challenges associated with direct detection methods. In the present study, a convenient strategy was employed to generate all possible CP acetates through reacting acetic anhydride with either glycerol in the presence of a chloride source or the corresponding CPs, such as 3-chloro-, 1,3-dichloro-, 2-chloro-, and 1,2-dichloropropanols, allowing for the identification of the individual CP acetates and assignment of their mass spectral fragmentations. Mass spectral fragmentations were confirmed through the use of the isotopic signature of chlorine in addition to the isotope labeling experiments performed using isotopically labeled precursors, such as [¹³C-U₃] glycerol, [¹³C-U₄] acetic anhydride, [¹³C-2,2'] acetic anhydride, and [d₅] 3-monochloropropane-1,2-diol (3-MCPD) as reactants. Such studies have indicated that all CP esters can undergo two general fragmentations under electron impact (EI) conditions, one generating the acylium ion at m/z 45 and the other generating a chlorinated cyclic acyloxonium ion at m/z 135.6. Considering the fact that such ions can also be generated from any fatty acid containing CP esters after undergoing McLafferty rearrangement, the ion at m/z 135.6 can therefore be considered as a universal marker for the presence of CP esters undergoing EI fragmentation. Furthermore, these studies have also indicated the formation of ions characteristic of CP diesters, monoesters, and dichloro esters.

Toxicology, occurrence and risk characterisation of the chloropropanols in food: 2-monochloro-1,3-propanediol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol

Great attention has been paid to chloropropanols like 3-monochloro-1,2-propanediol and the related substance glycidol due to their presence in food and concerns about their toxic potential as carcinogens. The other chloropropanols 2-monochloro-1,3-propanediol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol have been found in certain foods, but occurrence data are generally limited for these compounds. 1,3-dichloro-2-propanol has the most toxicological relevance showing clear carcinogenic effects in rats possibly via a genotoxic mechanism. The dietary exposure to 1,3-dichloro-2-propanol is quite low. Calculated "Margins of Exposure" values are above 10,000. It is concluded that the 1,3-dichloro-2-propanol exposure is of low concern for human health. The toxicology of 2,3-dichloro-1-propanol has not been adequately investigated. Its toxicological potential regarding hepatotoxic effects seems to be lower than that of 1,3-dichloro-2-propanol. Limited data show that 2,3-dichloro-1-propanol occurs only in trace amounts in food, indicating that exposure to 2,3-dichloro-1-propanol seems to be also of low concern for human health. The dietary 2-monochloro-1,3-propanediol burden appears to be lower than that of 3-monochloro-1,2-propanediol. An adequate risk assessment for 2-monochloro-1,3-propanediol cannot be performed due to limited data on the toxicology and occurrence in food. This article reviews the relevant information about the toxicology, occurrence and dietary exposure to the chloropropanols 2-monochloro-1,3-propanediol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol.

Determination of seven glycidyl esters in edible oils by gel permeation chromatography extraction and liquid chromatography coupled to mass spectrometry detection

A method based on a gel permeation chromatography (GPC) extraction procedure combined with an additional cleanup by solid-phase extraction (SPE) on silica gel and liquid chromatography-mass spectrometry (LC-MS) detection has been validated for the analysis of seven glycidyl esters (GEs) including glycidyl laurate, myristate, palmitate, stearate, oleate, linoleate, and linolenate in various edible oils. This method was conjointly developed and validated by two different laboratories, using two different detection systems, a LC time of flight MS (LC-ToF-MS) and a LC triple-quadrupole MS (LC-MS/MS). The extraction procedure allowed targeting low contamination levels due to a highly efficient matrix removal from the 400 mg oil sample loaded on the GPC column and is suitable for routine analysis as 24 samples can be extracted in an automated and reproducible way every 12 h. GPC extraction combined with SPE cleanup and LC-MS/MS detection leads to a limit of quantification in oil samples between 50 and 100 μg/kg depending on the type of glycidyl ester. Recoveries ranged from 68 to 111% (average = 93%). Quantification was performed by automated standard addition on extracts to compensate matrix effects artifacts. To control recoveries of each sample four isotopically labeled GEs ((13)C(3) or (13)C(4)) were included in the method.

Formation mechanisms of monochloropropanediol (MCPD) fatty acid diesters in refined palm (Elaeis guineensis) oil and related fractions

Monochloropropanediol (MCPD) fatty acid esters are process contaminants generated during the deodorisation of edible oils. In particular, MCPD diesters are found in higher abundance in refined palm oil than other edible oils. In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure acylglycerols in the presence or absence of either organic or inorganic chlorine-containing compounds. Results showed that the bulk of MCPD diesters are formed above 200°C through the reaction of organochlorines with triacylglycerols (TAG). Additional experiments confirmed that this reaction can be initiated during palm oil deodorisation by hydrogen chloride (HCl) gas evolved through the thermal degradation of organochlorines present in the oil. Therein, the majority of the ultimately produced MCPD diesters are the result of HCl reacting with TAG, via protonation, followed by the elimination of a fatty acid residue. Two possible MCPD diester formation mechanisms are highlighted, both of which involve acyloxonium ion reactive intermediates. Investigations with pure TAG regio-isomers showed that MCPD ester formation is regioselective and the sn-1(3) position of the glycerol backbone is favoured.

Glycidyl esters in refined palm (Elaeis guineensis) oil and related fractions. Part II: practical recommendations for effective mitigation

In a previous work, it was shown that at high temperatures (up to 280°C) glycidyl esters (GE) are formed from diacylglycerols (DAG) via elimination of free fatty acid (FFA). In the present study, the impact of DAG content and temperature on the formation of GE using a model vacuum system mimicking industrial edible oil deodorization is investigated. These deodorization experiments confirmed that the formation of GE from DAG is extensive at temperatures above 230-240°C, and therefore, this value should be considered as an upper limit for refining operations. Furthermore, experimental data suggest that the formation of GE accelerates in particular when the DAG levels in refined oils exceed 3-4% of total lipids. Analysis of the lipid composition of crude palm oil (CPO) samples allowed the estimation that this critical DAG content corresponds to about 1.9-2.5% of FFA, which is the conventional quality marker of CPO. Moreover, high levels (>100ppm) of GE were also found in palm fatty acid distillate samples, which may indicate that the level of GE in fully refined palm oils also depends on the elimination rate of GE into the fatty acid distillate.